A variety of electronic devices employ touch screens or touch panels to detect the presence and location of a touch within a display area of the electronic device, generally by a finger, hand, or other object. Such electronic devices include mobile phones, internet devices, portable game consoles, portable readers, music players, navigation devices, appliances, automation and control electronics, laptop computers, television screens, and the like. Touch screens allow for direct interaction with what is displayed on the screen where it is displayed, rather than indirect interaction through a mouse or separate touch pad. Touch screens also enable such interaction without requiring any intermediate devices, such as a stylus that must be held in a user's hand.
There are a number of touch screen technologies, and from among these various technologies, acoustic touch screen technology has emerged as a durable and accurate technology that functions even when the screen itself is dirty or scratched. Acoustic touch screen technology involves using acoustic transducers to convert the mechanical or acoustic energy generated by a physical contact with a touch screen substrate into an electronic signal. Hardware and software that is operatively connected to the transducers then analyzes the electronic signal to determine the location of the contact. Because no acoustic energy is generated when the finger or other object lies motionless against the screen, acoustic sensing technology is unable to detect when a finger is held against the screen after an initial contact.
One proposed solution to this problem includes a capacitive sensing mechanism that employs conductive wire to connect a number of capacitors in series along one or more borders of the touch screen substrate. Each of the capacitors includes two electrodes that are spaced a distance apart. When a user touches a surface of the screen substrate with an object such as a finger, the electrodes to move towards one another, thereby reducing the gap between the electrodes and causing a capacitance variation that can be converted into a binary signal representing a “hold” or “release” action in relation to a contact with the touch screen. Further, to shield against electromagnetic interference from both the environment and an associated display, known touch screen systems employ a number of conductive and insulating layers deposited upon the screen substrate.
While the existing approach allows the touch screen system to sense when an object is in continuous contact with the screen, it has many shortcomings. For instance, using soldered wires to interconnect the capacitors in series is a time-consuming manual process that introduces variance into the system and reduces the quality and reliability of the hold-and-release sensing. In addition, depositing numerous conductive and insulating layers onto the screen substrate to adequately shield against noise caused by electromagnetic radiation consumes a great deal of material, much of which is lost during the printing process, rendering the manufacturing process unduly wasteful and expensive. Further, existing acoustic and capacitive touch screen systems have required dedicated connectors to link both the acoustic and the capacitive sensing components on the screen substrate with the processing components on an associated control board. These dual connectors enlarge the space required for the touch screen system and render the system too bulky for many compact electronic devices.
It is against this background that the teachings herein have been developed.